11 Miss. Code. R. 6-1.2.3
The WQBEL process is a means of determining the available assimilative capacity of a water body and setting WQBELs utilizing appropriate procedures for simulation and prediction of water quality impacts. This process will be used unless the Department determines there are adequate data to support a determination that the receiving water body currently meets water quality standards and will continue to meet water quality standards with the discharge. Computer models utilized include those approved and supported by the Commission and/or EPA. The methodologies used for the WQBEL process are found in Exhibit A to this Subchapter and in Rule 1.2.4 of this chapter. In the event the receiving water body's minimum flow value used for allocation purposes is zero, permit limitations shall be modeled with the flow equal to the effluent for conventional pollutants unless otherwise provided in these regulations. The minimum CBOD model input for WQBEL permit limit determination will be equivalent to the estimated background conditions for streams (2.0 CBODu) as indicated in Exhibit A.I.J.2. The permittee may provide the necessary scientific information to support a less stringent limit.
Unless actual data or circumstances indicate otherwise, computer modeling is suitable for developing effluent limitations in water bodies for the cases that follow:
The State's specific conventional point source water quality modeling and WLA criteria, including specific chlorine and ammonia requirements, are located in Exhibit A to this Subchapter which is incorporated herein and adopted by reference.
Calibration modeling and/or verification modeling and/or a water quality field assessment (including physical, chemical, and/or biological water quality surveys) may be required for the determination of WQBELs because of the consideration of factors as follows: the complexity of the receiving water body, magnitude and impact or potential impact of the discharge, amount of available data, aquatic life and/or human health concerns, and any other factor deemed necessary by the Permit Board to protect water quality. The applicant may be required to provide the necessary information.
The WQBEL process may be utilized to determine new discharge permit limits and to evaluate permit renewals when: a. the Department determines existing water quality data is insufficient to evaluate expected water quality impacts, b. the Department determines the available assimilative capacity of the water body is being completely utilized, either alone or in combination with other discharges (including both point and nonpoint sources), c. the Department determines water quality standards are being violated, or d. when the permittee so chooses (except for the purpose of delaying implementation of a particular permit limit). The Department may reissue permits which contain existing permit requirements if the data are adequate to support that the receiving water body currently meets and will continue to meet water quality standards.
When a WQBEL process is determined to be necessary, the analysis shall consider and determine WQBELs for the permit applicant considering all affected discharger(s) to the receiving water body, including both point and nonpoint sources.
When an applicant is developing and/or conducting a verified and/or calibrated model and/or conducting a water quality field assessment in the WQBEL process for submittal to the Department, the applicant shall:
11 Miss. Code. R. 6-1.2.3